Carburetor



Nov. 16, 1954 E. OLSON 2,694,560

CARBURETOR Filed Aug. 9, 1949 I 3 Sheets-Sheet l Nov. 16, 1954 E. OLSON2,694,560

CARBURETOR Filed Alig. 9, 1949 3 Sheets-Sheet 5 INVENTOR. Elmer OlsonAffomeys United States Patent CARBURETOR Elmer Olson, Rochester, N. Y.,assignor to General Motors Corporation, Detroit, Mich., a corporation ofDelaware Application August 9, 1949, Serial No. 109,347

Claims. (Cl. 261-41) This invention relates to carburetors for internalcombustion engines, particularly for automotive use and it is an objectof the invention to provide a carburetor of improved design which is ofsimple and durable construction, inexpensive to manufacture and willbring about gfli cient operation of the engine under all operating con-One specific object of the invention is to minimize the heating of thefuel in the float chamber, and also to prevent the vaporization of fuelin the passages leading from the float chamber to the fuel inlets whichintroduce fuel into the mixture, or intake passage, particularly whenthe engine is stopped after operation in warm weather.

A further specific object of the invention is to provide fuel passagesfor supplying fuel to the mixture passage which are so arranged thatthere is no appreciable lag in fuel flow nor appreciable momentaryreduction in engine speed at the time of transfer from operation of theengine on the idle fuel system to operation on the main fuel inlet.

An additional specific object of the invention is to provide means forpermitting the escape of fuel vapor from the bottom of the acceleratingpump cylinder so as to prevent any vapor which might collect below thepump piston from forcing fuel out of the pump cylinder into the intakepassage.

A still further object of the invention is to provide means forpreventing the formation and collection of vapor bubbles in the fuelsupply passage during the idling of the engine so that the idling fuelsupply is even and continuous and the engine operation during the periodof transition from idling to operation under load is smooth and notirregular, as would be the case if such vapor bubbles formed andcollected in the fuel passage to any appreciable extent during theidling operation.

Another purpose of the invention is to provide improved mechanism foroperating the choke and throttle valves which includes means foryieldingly holding an unbalanced choke valve in closed position, meansfor positively moving the choke toward closed position in the event thatit becomes stuck in fully open position and for increasing the openingof the throttle as the choke is closed so that I the idling speed of theengine is increased as the choke is moved toward closed position.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

Fig. 1 is a sectional view of the carburetor on line 11 of Fig. 2.

Fig. 2 is a sectional view on the line 2-2 of Fig. 1.

Fig. 3 is a sectional view on the line 33 of Fig. 1 and is drawn to alarger scale.

Fig. 4 is a sectional view on the line 44 of Fig. 1.

Fig. 5 is a fragmentary sectional view on the line 5+5 of Fig. 2.

Fig. 6 is an enlargement of a portion of Fig. 5.

Fig. 7 is a sectional view on the line 7-7 of Fig. 6.

Fig. 8 is a sectional view on the line 8-8 of Fig. 4.

Fig. 9 is a top plan view of the base casting 30.

Fig. 10 is a fragmentary sectional view on the line Iii-10 of Fig. 9.

Fig. 11 is a sectional view on the line 11-11 of Fig. 9.

Fig. 12 is an enlargement of a view on line 1212 of Fig. 11.

Fig. 13 is an enlargement of that portion of Fig. 11 within the circle13.

Fig. 14 shows a central portion of Fig. l drawn to a larger scale.

Referring to Fig. 1, the carburetor has four castings, 30, 31, 32 and33. Casting is a support member attachable to the engine intake andsupports the float bowl 31 to which is secured the casting 32, which isa cover for the bowl, while casting 33 is secured to and depends fromthe cover 32 and the main fuel supply passage is formed therein. Thebase 30 has holes 34 to receive screws for attaching the carburetor tothe manifold with a gasket between. Screws which pass through holes 36(Fig. 9) in base 30 and into threaded holes 36a in bowl 31 (Fig. 8)secure the bowl and base together with a gasket 37 (Fig. 1) betweenthem. As shown in Figs. 1' and 8, the bowl 31 is provided with deepgrooves 38 and 39 and with shallower grooves 40 and 41 which reduce thearea of contact of bowl 31 with the gasket 37. The grooves tend toprevent displacement of the gasket because of shrinkage and the grooves40 and 41 have other functions to be described later.

Cover 32 is secured to the bowl 31 by screws received in tapped holes43. A gasket 44 (Fig. l) is located between cover 32 and bowl 31. Thearea of the surfaces of the bowl and cover in contact with the gasket 44being relatively narrow, the transfer of heat between them is relativelylow. The member 33 is secured to cover 32 by a screw 45 (Fig. 5) with asmall gasket 46 between them and member 33 has a lug 47 which enters anotch 48 in cover 32 when the parts are assembled to prevent relativemovement. Since the area contacted between cover 32 and member 33 isrestricted, the transfer of heat to the member 33 is relatively low.Thus, the transfer of heat from the engine to the bowl and other partsof the carburetor is kept as low as possible. A substantial amount ofheat is dissipated from the bowl 31 to the surrounding atmosphere underthe hood of the automobile from the relatively large outer wall of thebowl and the interior wall thereof is cooled by vaporization of the fuelas it is introduced into the intake passage.

The main fuel inlet for supplying fuel to the intake passage dischargesfuel within a primary venturi tube 50 supported by ribs 52 at the centerof the intake passage and the primary venturi extends into a secondaryventuri 51, which is the wall of the intake passage and is also theinterior wall of the float bowl.

Referring to Fig. 1, the fuel is supplied to the float bowl throughcoupling to the passage 61 and flows from this passage into the bowlthrough a bushing 62 providing a valve seat 63 for a float valve 64having the conventional flat sides 65 and operable by a finger 66integral with a lever 67 pivoted on rod 68, supported by two lugs 69,extending downwardly from the cover 32. As shown in Fig. 2, lever 67 isattached to floats 70. The mechanism described maintains a substantiallyconstant level of fuel in the bowl, and a finger 71 integral with lever67 engages the bushing 62, if for any reason the float chamber isemptied so as to prevent the floats striking the bottom of the floatchamber and also to prevent the floats moving downwardly enough topermit the valve 64 to fall out of the bushing into the float chamber.

As shown in Figs. 1 and 5, the main fuel supply passage 75 through whichfuel flows from the bowl to the intake passage, is formed in the member33. Admission of fuel to the passage 75 is controlled by the mainmetering plug 76.

Under certain operating conditions, fuel is also admitted to the passage75 through two notches 77 formed in a horizontal projecting portion ofthe member 33, as shown in Fig. 7. These notches communicate with apassage 77a (Fig. 6), which admits fuel to a space connected by apassage 79 with the passage 75, the flow through passage 79 beingcontrolled by a metering plug 78. Flow through passage 77a is controlledby a ball check valve 83 which, under operating conditions where theintake suction is low, as when operating at wide open throttle andrelatively low speed, for example, is positioned to open the passage77a, so that the amount of fuel flowing into passage 75 is somewhatincreased and the mixture enriched, as is desirable under suchconditions. Under those operating conditions wherethe intake suction ishigh, as for example when operating with partially open throttle andlight load, a leaner mixture is desirable and the additional supply offuel through the passage 79 is not necessary. Under such conditions, thecheck valve 83 is moved to position to close the passage 79.

. When the suction is low, a spring 81 moves rod 82 downwardly and holdsthe ball 83 in the position shown in Fig. 8, with the passage 77a openagainst the action of spring 84 which is positioned below the ball in abushing 85. Rod 82 is connected to the hollow piston 87 operable byspring 81 and slidable in-a cylinder 86 formed in a part of the cover 32and to which the manifold suction is communicated through a passage 88,which connects with passage 89 in the bowl casting 31 (Fig. 2),communicating with groove 40 also in the bowl casting, as shown in Fig.8. The groove 40 connects with the passage 90 in the casting 30, asshown in Fig. and when the carburetor is installed, the manifold suctionis communicated to passage 90 through the passage 91.

If the manifold vacuum is relatively high, as on part throttleoperation, it is effective to lift the piston and rod 82 against theforce of spring 81 so that check valve 8; will be moved by spring 84 toclose the passage As shown in Figs. 1 and 14, extending across the airintake 95 and integral therewith is a conduit 96 in which a fuel passageis provided having parts 97, 98 and 99 of different diameters, the part97 connecting with the main fuel passage 75. A tube 100 is positioned inthe part 98 of the conduit 96 and this tube has a restriction 101 at itsright end. A relatively large air bleed 102, formed in a bushing 103 andsmaller bleeds 104 and 105 admit air to the fuel conduit 96, as shownbest in Fig. 14. The part 99 of the fuel conduit connects with a passage106, extending downwardly in the casting 31, which at its lower endconnects with the groove 41, as shown in Fig. 8, and this grooveconnects with the bore 107 in the base 30, as shown in Fig. 11. The bore107 is connected by passage 108 with the intake passage posterior to thethrottle 110, which is supported on a rotatable shaft 111. Flow throughpassage 108 is controlled by the manually adjustable valve 112, held inany set position by the friction spring 113. Connecting the intakepassage with the bore 107 slightly anterior to the throttle, when inclosed position, are three small orifices 115, 116 and 117, for apurpose to be later set forth.

During idling of the engine when the throttle is substantially or nearlyclosed, the high suction which is maintained posterior thereto iscommunicated to the fuel in passage 75 through the above describedarrangement of passages. This will cause fuel to flow from passage 75through passage 97, tube 100, passages 99, 106, 107 and 108 into theintake. A solid stream of fuel flows through the passages 75 and 97during idling, but this fuel is mixed with air which enters the bleedholes 102, 104, 105 and 120 to form a rich mixture for idling and thismixture is carried from that point on through the previously mentionedpassages into the intake, the quantity of idling mixture being regulatedby adjustment of the valve 112. Some additional air will flow into themixture as it is drawn through bore 107 through the holes 115, 116 and117 if the throttle is closed to such an extent thatsuch holes areanterior to the throttle.

During idling there is practically no flow of air through the primaryventuri tube and no introduction of fuel into such tube. However, as thethrottle is moved toward its open position from the idling position,shown in Fig. 11, the flow of air through .the primary venturi will beincreased and the suction will ultimately become great enough to effecta flow of fuel from the main fuel inlet 122 which connects with the part98 of the fuel conduit immediately adjacent the end of the passage 97directly below the air bleeds 102, 104 and 105, and has a bushing 121therein, provided with a restriction 120 which aids in breaking up thefuel which is discharged into the primary venturi.

"The flow of fuel from the main inlet 122 begins before the flow ofidling mixture ceases, but as the 3 throttle is progressively opened,the suction in the primary venturi will become so great by comparisonwith the suction at the end of passage 108 that flow from passage 108will cease and instead, there will be a flow from the intake intopassage 108 and a reverse flow from that point back through the idlingmixture passages to the main fuel inlet.

In carburetors of the prior art there has been some difficultyencountered at the time of transfer of operation from the idling systemto the main fuel supply due to a momentary leaning of the mixture atthis time. This was due to the fact that while the idling systemfunctioned, the fuel for the main fuel inlet was maintained at anappreciable distance from such inlet, so

that before the main fuel inlet began to function, the fuel had to movethrough this distance. Due to its inertia, this movement of the fuel tothe main inlet required an appreciable interval of time so that therewas a slight lag in the fiow of fuel from the main inlet with respect tothe flow of air through the intake passage. In the device disclosedherein, the above described difficulty is substantially eliminatedbecause a solid column of fuel is maintained in the passages and '97 toa point immediately adjacent the main fuel inlet. Therefore, when themain inlet begins to function, the fuel does not have to be movedthrough any appreciable distance. It is already maintained at a pointimmediately adjacent the fuel inlet 122 before the latter starts tofunction.

The bleed holes 102, 104 and not only admit air to form the idlingmixture, but also prevent the formation of bubbles, of sufiicient sizeto cause any appreciable irregularity in flow through the idling passagewhich otherwise might tend to occur under some operating conditions, ifthe several orifices were not provided to supply air to the spaceposterior to the end of passage 97. The admission of air at relativelyhigh velocity through the several orifices 102, 104, 105 and aids ineffecting a thorough atomization of the fuel which is discharged fromthe passage 97 to form a homogeneous idling mixture.

As the throttle begins its opening movement from the position shown inFig. 11, the holes 115, 116 and 117 are successively brought on the highsuction side of the throttle. This action will progressively increasethe suction effective on the idling fuel supply passages and slightlyincrease the idling mixture.

As already set forth, the device disclosed is formed of three separatecastings separated by gaskets and has other means to minimize theheating effect of the engine on the fuel in chamber 31 and the variousfuel passages. In addition, the main fuel supply passage is so arrangedthat there will be substantially no vaporization of fuel in the passageafter the engine has stopped, even at the highest temperaturesencountered in summer operation.

In conventional down-draft carburetors of the prior art where the fuelpassages leading to the main and idling fuel inlets are formed in thewall of the float chamber, vaporization of fuel in these passages, orwhat is known as percolation has caused very considerable trouble withthe highly volatile fuels now in use. The formation of fuel vapor in thefuel will create sufficient pressure to cause discharge of fuel in thefuel passages between the vapor and the fuel inlets which supply fuel tothe intake passage. This process may be repeated many times if thetemperature is high and may result in emptymg the float chambercompletely. By providing the fuel passage 75 which extends downwardlyinto the fuel chamber from above the fuel and the passage 97, thatsupplies fuel to the main and idling fuel inlets, lying entirely abovethe float chamber 31, the formation of vapor in the fuel passages issubstantially prevented. If the fuel in chamber 31 gets hot enough toform fuel vapor bubbles, they will not enter the passage 75, and sincepassage 75 extends upwardly to the passage 97, there will besubstantially no vaporization of fuel in the passage 75, itself. Theonly vaporization of fuel in the bowl 31 will be adacent the bottom wallthereof and passage 75 is sufficiently above the bottom of the bowl tobe out of the area where the heat may be enough to cause somevaporizatlon.

Also fuel passages 75 and 97 are formed in the upper casting 32 whichforms the air intake and cover for the float chamber. This casting isseparated from the float chamber by a gasket so that there is nometallic conductrvity between the manifolds and the passages 75 and 97'.This, of course, reduces the heating of such passages, but since thepassages 75 and 97 are entirely above or extend upwardly from the fuellevel, if under any circumstances such passages get hot enough to formvapor, such vapor forms above the level of fuel and merely passes intothe intake without forcing any liquid fuel in said intake, so that thereis no percolation.

At the left of Fig. 1 there is shown mechanism for operating the shaft130 which supports a choke valve 131 and also means through the mediumof which the position of the choke valve controls the idling position ofthe throttle under certain circumstances.

Also there is disclosed a cylinder 132 which with its associatedmechanism constitutes an accelerator pump for supplying additional fuelwhen the throttle is opened to increase the speed. Neither the chokeoperating mechanism nor the accelerator pump constitute any part of theinvention which is claimed in this application and for this reason suchdevices are not described specifically herein.

It may be said, however, that the cylinder 132 of the accelerator pumpis in communication with the space above the fuel in the float chamber31 and in order to provide a vent for this space so as to maintaintherein a pressure which approaches that of the atmosphere, a tube 134connects the top of cylinder 132 with the intake passage adjacent theair inlet end thereof anterior to the choke valve. Because of the slightrestriction to the admission of air imposed by the air cleaner, thistube 134 is effective to maintain in the float chamber a pressure justbarely less than that of the atmosphere. This vent forms no part of thepresent invention and is of the type now conventionally used in the art.

While the embodiment of the present invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. A carburetor for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passageprovided with a throttle valve for controlling the how of combustiblemixture therethrough, main and idling fuel inlets for supplying fuel tothe mixture passage, an inverted U-shaped passage for supplying fuel tosaid inlets, said passage having a leg extending downwardly into thefuel chamber and through which only fuel flows, said passage havingmeans below the level of fuel in said chamber for admitting fuel theretoso that liquid fuel stands in said leg when the engine is inoperativeand flows therethrough when the engine is running, the other leg of suchpassage extending downwardly to supply idling fuel to the idling fuelinlet, a horizontal connecting passage located above the level of fuelin the fuel chamber for connecting the upper ends of the legs of theU-shaped passage and connecting with the main fuel inlet to supply fuelthereto and a plurality of orifices admitting air to said connectingpassage adjacent the point of connection of the main fuel inlettherewith so as to atomize the fuel flowing therethrough and to effect asubstantially even flow of fuel for idling when the idling fuel systemis in operation, said orifices being of different size and the larger ofsaid orifices being substantially coaxial with the main fuel inlet.

2. A carburetor for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passageprovided with a throttle valve for controlling the flow of combustiblemixture therethrough, main and idling fuel inlets for supplying fuel tothe mixture passage, an inverted U-shaped passage for supplying fuel tosaid inlets, said passage having one leg extending downwardly into thefuel in said fuel chamber so as to be entirely surrounded with fuel andhaving no metallic contact with said fuel chamber, through which onlyfuel flows, another leg extending downwardly to supply idling fuel tothe idling fuel inlet and a horizontal passage located above the fuellevel in the fuel chamber for connecting the upper ends of thedownwardly extending legs of said fuel passage and communicating withthe main fuel inlet, a plurality of fuel inlets in said first named Uleg of the passage positioned below the level of fuel in the fuelchamber for admitting fuel thereto, said fuel inlets being open when theengine is inoperative and during engine operation when the enginesuction is low and means also having no metallic contact with the fuel 6chamber for automatically closing one of said fuel inlets when theengine suction is relatively high.

3. A carburetor for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passageprovided with a throttle valve for controlling the flow of combustiblemixture therethrough, main and idling fuel inlets for supplying fuel tothe mixture passage, an inverted U-shaped passage for supplying fuel tosaid inlets, said passage having one leg extending downwardly into thefuel in said fuel chamber so as to be entirely surrounded with fuel andhaving no metallic contact with said fuel chamber, through which onlyfuel flows, another leg extending downwardly to supply idling fuel tothe idling fuel inlet and a horizontal passage located above the fuellevel in the fuel chamber for connecting the upper ends of thedownwardly extending legs of said fuel passage and communicating withthe main fuel inlet, a plurality of fuel inlets in said first named legof the passage positioned below the level of fuel in the fuel chamberfor admitting fuel thereto, means for maintaining both of said inletsopen when the engine is inoperative and during engine operation when theengine suction is low and suction operated means also having no metalliccontact with the fuel chamber for rendering said last named meansineffective and causing the closing of lone}:1 of said fuel inlets whenthe engine suction is relatively 4. A carburetor for an internalcombustion engine having, in combination, a constant level fuel supplychamber, an intake passage provided with a throttle valve forcontrolling the flow of combustible mixture therethrough, main andidling fuel inlets for supplying fuel to the mixture passage, aninverted U-shaped passage for supplying fuel to said inlets, saidpassage having a leg extending downwardly into the fuel chamber andthrough which only fuel flows, said passage having means below the levelof fuel in said chamber for admitting fuel thereto so that liquid fuelstands in said leg when the engine is inoperative and flows therethroughwhen the engine is running, the other leg of such passage extendingdownwardly to supply idling fuel to the idling fuel inlet, a horizontalconnecting passage located above the level of fuel in the fuel chamberfor connecting the upper ends of the legs of the U-shaped passage andconnecting with the main fuel inlet to supply fuel thereto, arestriction in the horizontal passage posterior to the main fuel inlet,said horizontal passage posterior to the restriction being larger thanthe restriction, and a plurality of orifices admitting air to saidhorizontal passage adjacent said restriction to atomize the fuel in saidpassage and including a relatively large orifice anterior to saidrestriction and substantially coaxialwith the main fuel inlet.

5. A carburetor for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passageprovided with a throttle valve for controlling the How of combustiblemixture therethrough, main and idling fuel inlets for supplying fuel tothe mixture passage, an inverted U-shaped passage for supplying fuel tosaid inlets, said passage having a leg extending downwardly into thefuel chamber and through which only fuel flows, said passage havingmeans below the level of fuel in said chamber for admitting fuel theretoso that liquid fuel stands in said leg when the engine is inoperativeand flows therethrough when the engine is running, the other leg of suchpassage extending downwardly to supply idling fuel to the idling fuelinlet, a horizontal connecting passage located above the level of fuelin the fuel chamber for connecting the upper ends of the legs of theU-shaped passage and connecting with the main fuel inlet to supply fuelthereto, a restriction in the horizontal passage posterior to the mainfuel inlet, said horizontal passage posterior to the restriction beinglarger than the restriction, and a plurality of orifices admitting airto said horizontal passage adjacent said restriction to atomize the fuelin said passage and including a relatively large orifice anterior tosaid restriction and substantially coaxial with the main fuel inlet andtwo smaller orifices on opposite sides of the larger orifice.

(References on following page) 7 References Cited in the file of thispatent N mber UNITED STATES PATENTS Number Name Date 2,307,486 1,909,389Ball et a1 May 16, 1933 5 2,327,300 2,017,890 Bracke Oct. 22, 19352,393,125 2,035,636 Chandler Mar. 31, 1936 2,397,392 2,065,167 Wirth eta]. Dec. 22, 1936 2,407,535 Carlson et al Sept. 10, 1946 2,087,293 OlsonJuly 20, 1937 2,415,491 Hieger Feb. 11, 1947 2,162,056 Bracke June 13,1939 10 2,426,272 Hennemann Aug. 26, 1947 2,215,683 Wirth Sept. 24, 1940

